Late Glacial and Early Holocene cyclic changes in paleowind conditions and lake levels inferred from diatom assemblage shifts in Laguna Potrok Aike sediments (southern Patagonia, Argentina)

ZIMMERMANN, C.; JOUVE, G. ; PIENITZ, R.; FRANCUS, P.; MAIDANA N. I.

PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2015 vol. 427 p. 20 - 31

0031-0182

PASADO isamultidisciplinary Potrok Aike Sediment Archive Drilling prOject,whichwasconducted from2008 to 2013, focusing on the sedimentary record of the volcaniccrater maar Laguna Potrok Aike (52°S, 70°W, 116masl) in southern Patagonia,Argentina. It represents one of the few non-glacial and extra-Andean sedimentarchives studied so far on the continental landmass between subtropical SouthAmerica and Antarctica that covers the entire Holocene and the Late Glacial. Inthis study, a high-resolution diatom analysis of the Late Glacial time intervalsituated between 15.60 and 10.51 ka cal. BP was performed on the PASADOsediment core. This period is of particular interest as it encompasses theAntarctic Cold Reversal (ACR), as well as the Younger Dryas (YD) chronozone. Tobetter refine the variability of environmental and climatic conditions of thisLate Glacial time interval, we combined our data with those of amicrosedimentological analysis conducted on the same sediments and for the sameperiod to infer changes in lake level and water column stratification. Ourstudy revealed that diatoms are an ideal proxy to complementmicrosedimentological analyses by providing important independent informationon the past limnological dynamics of Laguna Potrok Aike and the paleoclimaticconditions that prevailed during the Late Glacial in the study area and allowsa new way of explaining shifts in the position of Southern Hemisphere WesterlyWinds (SWW) during the Late Glacial. Peaks of planktonic diatoms, particularly Cyclostephanospatagonicus, correspond to previously detected total organic carbon (TOC),Ca/Si, Ca andMn peaks and support the hypothesis that relatively high lakelevels and weaker SWW have prevailed during  the Late Glacial. Moreover, a cyclic pattern,observed both in the biological and geochemical indicators, suggests at least fiveshifts in the position of the SWW from the beginning of the ACR to the end ofthe YD. The periodicity of these shifts seems to be related to Antarcticice-sheet discharge (AID) events in the Scotia Sea that coincide with enhancediceberg flux from the Antarctic ice-sheet.